The present invention relates to an electrophotographic photoreceptor which contains a novel hydrazone compound.
Hitherto, inorganic photoconductive substances such as selenium, cadmium sulfide, zinc oxide and silicon have been known for photoreceptors of electrophotographic system and widely studied and some of them have been put to practical use. Recently, organic photoconductive materials have also been intensively studied as electrophotographic photoreceptors and some of them have been practically used.
In general, inorganic materials are unsatisfactory, for example, selenium photoreceptors have problems such as deterioration in heat stability and characteristics due to crystallization and difficulty in production and cadmium sulfide photoreceptors have problems in moisture resistance, endurance and disposal of industrial waste. On the other hand, organic materials have advantages such as good film-formability, excellent flexibility, light weight, high transparency and easy designing of photoreceptors for wavelength of wide region by suitable sensitization. Thus, organic materials have increasingly attracted attention.
Photoreceptors used in electrophotographic technique are required to possess the following fundamental properties, namely, (1) high chargeability for corona discharge in the dark place, (2) less leakage (dark decay) of the resulting charge in the dark place, (3) rapid release (light decay) of charge by irradiation with light, and (4) less residual charge after irradiation with light.
Extensive research has been made on photoconductive polymers as organic photoconductive substances including polyvinylcarbazole, but these are not necessarily sufficient in film-formability, flexibility and adhesion and besides these cannot be said to have sufficiently possessed the above-mentioned fundamental properties as photoreceptor.
On the other hand, since organic low molecular photoconductive compounds generally do not have film-formability, suitable binders must be used in combination. These compounds are preferred in that properties of film and electrophotographic characteristics can be somewhat controlled by selection of the binders, but organic photoconductive compounds having a high compatibility with binders are limited and at present a few compounds are practically used as electrophotographic photoreceptors.
As mentioned above, various improvements have been made in making of electrophotographic photoreceptors, but none of photoreceptors which are satisfactory in the above-mentioned fundamental properties and have high endurance have not yet been obtained.